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  • 1
    Electronic Resource
    Electronic Resource
    Giant magnetoimpedance in layered FeSiB/Cu/FeSiB films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1816-1819 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoimpedance (GMI) effect has been studied in layered FeSiB/Cu/FeSiB films in the frequency range of 100 kHz–40 MHz. The field dependence of the GMI ratio shows that the GMI ratio increases with magnetic field Ha, reaching a positive maximum value at a certain field, and then gradually decreases to negative values. For the layered films with a Cu film width of 0.6 mm, the positive maximum GMI ratio is about 2%, which is smaller than the value of the negative GMI ratio (−6.6% at Ha=50 Oe) at a frequency of 5.2 MHz. With an increase of the Cu film width, a positive maximum GMI ratio of 4.5% and 13.5% is obtained for Ha=30 Oe and 5.2 MHz in the layered films with a Cu film widths of 1 and 1.3 mm respectively. In addition, all the layered films exhibit a large negative GMI ratio at a relatively large field and it is associated with the easy axis orientation of the layered films. The increase of the positive maximum GMI ratio with an increase of Cu film width at 5.2 MHz may be due not only to the effect by the increase of Cu film width, but also to the difference in the easy axis orientations of the layered FeSiB/Cu/FeSiB films. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338514
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  • 2
    Electronic Resource
    Electronic Resource
    On the collision rate of small particles in isotropic turbulence. II. Finite inertia case (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 1206-1216 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical experiments have been performed to study the geometric collision rate of heavy particles with finite inertia. The turbulent flow was generated by direct numerical integration of the full Navier-Stokes equations. The collision kernel peaked at a particle response time between the Kolmogorov and the large-eddy turnover times, implying that both the large-scale and small-scale fluid motions contribute, although in very different manners, to the collision rate. Both numerical results for frozen turbulent fields and a stochastic theory show that the collision kernel approaches the kinetic theory of Abrahamson [Chem. Eng. Sci. 30, 1371 (1975)] only at very large τp/Te, where τp is the particle response time and Te is the flow integral time scale. Our results agree with those of Sundaram and Collins [J. Fluid Mech. 335, 75 (1997)] for an evolving flow. A rapid increase of the collision kernel with the particle response time was observed for small τp/τk, where τk is the flow Kolmogorov time scale. A small inertia of τp/τk=0.5 can lead to an order of magnitude increase in the collision kernel relative to the zero-inertia particles. A scaling law for the collision kernel at small τp/τk was proposed and confirmed numerically by varying the particle size, inertial response time, and flow Reynolds number. A leading-order theory for small τp/τk was developed, showing that the enhanced collision is mainly a result of the nonuniform particle concentration that results from the interaction of heavy particles with local flow microstructures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869644
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  • 3
    Electronic Resource
    Electronic Resource
    Statistical mechanical descriptions of turbulent coagulation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 2647-2651 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fundamental tenet of statistical mechanics is that the rate of collision of two objects is related to the expectation value of their relative velocities. In pioneering work by Saffman and Turner [J. Fluid Mech. 1, 16 (1956)], two different formulations of this tenet are used to calculate the collision kernel Γ between two arbitrary particle size groups in a turbulent flow. The first or spherical formulation is based on the radial component wr of the relative velocity w between two particles: Γsph=2πR2〈|wr|〉, where wr=w⋅R/R, R is the separation vector, and R=|R|. The second or cylindrical formulation is based on the vector velocity itself: Γcyl=2πR2〈|w|〉, which is supported by molecular collision statistical mechanics. Saffman and Turner obtained different results from the two formulations and attributed the difference to the form of the probability function of w used in their work. A more careful examination reveals that there is a fundamental difference between the two formulations. An underlying assumption in the second formulation is that the relative velocity at any instant is locally uniform over a spatial scale on the order of the collision radius R, which is certainly not the case in turbulent flow. Therefore, the second formulation is not expected to be rigorously correct. In fact, both our analysis and numerical simulations show that the second formulation leads to a collision kernel about 25% larger than the first formulation in isotropic turbulence. For a simple uniform shear flow, the second formulation is about 20% too large. The two formulations, however, are equivalent for treating the collision rates among random molecules and the gravitational collision rates. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869777
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  • 4
    Electronic Resource
    Electronic Resource
    On the collision rate of small particles in isotropic turbulence. I. Zero-inertia case (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 266-276 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical experiments have been performed to study the geometric collision rate of finite-size particles with zero inertia (i.e., fluid elements) in isotropic turbulence. The turbulent flow was generated by the pseudospectral method. We argue that the formulation of Saffman and Turner [J. Fluid Mech. 1, 16 (1956)] for the average collision kernel is correct only under the assumptions that the particles are kept in the system after collision and allowed to overlap in space. This was confirmed, for the first time, by numerical experiments to within a numerical uncertainty as small as 1%. Finite corrections to the Saffman and Turner result must be made if one applies the theory to actual coagulation process where particles are not allowed to overlap before collision and particles are removed from a given size group after collision. This is due to the fact that Saffman and Turner assumed a uniform, time-independent concentration field in their formulation of the average collision kernel, while in the actual modeling of population evolution the particle number concentration changes in time and may be locally nonuniform as a result of a biased removal process due to spatially nonuniform coagulation rates. However, the quantitative level of the deviations from the Saffman and Turner result remain to be explained. Numerical experiments in simple shear flow were also conducted to elaborate our findings. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869565
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  • 5
    Electronic Resource
    Electronic Resource
    A resolvable subfilter-scale model specific to large-eddy simulation of under-resolved turbulence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 2602-2610 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large-eddy simulation (LES) of boundary-layer flows has serious deficiencies near the surface when a viscous sublayer either does not exist (rough walls) or is not practical to resolve (high Reynolds numbers). In previous work, we have shown that the near-surface errors arise from the poor performance of algebraic subfilter-scale (SFS) models at the first several grid levels, where integral scales are necessarily under-resolved and the turbulence is highly anisotropic. In under-resolved turbulence, eddy viscosity and similarity SFS models create a spurious feedback loop between predicted resolved-scale (RS) velocity and modeled SFS acceleration, and are unable to simultaneously capture SFS acceleration and RS–SFS energy flux. To break the spurious coupling in a dynamically meaningful manner, we introduce a new modeling strategy in which the grid-resolved subfilter velocity is estimated from a separate dynamical equation containing the essential inertial interactions between SFS and RS velocity. This resolved SFS (RSFS) velocity is then used as a surrogate for the complete SFS velocity in the SFS stress tensor. We test the RSFS model by comparing LES of highly under-resolved anisotropic buoyancy-generated homogeneous turbulence with a corresponding direct numerical simulation (DNS). The new model successfully suppresses the spurious feedback loop between RS velocity and SFS acceleration, and greatly improves model predictions of the anisotropic structure of SFS acceleration and resolved velocity fields. Unlike algebraic models, the RSFS model accurately captures SFS acceleration intensity and RS–SFS energy flux, even during the nonequilibrium transient, and properly partitions SFS acceleration between SFS stress divergence and SFS pressure force. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388053
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation and Properties of 2D C/SiC-TaC Composites (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 368-372 (Feb. 2008), p. 1771-1773 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ultra high temperature ceramic matrix composites (UHTCC) are being considered as the mostpromising materials for leading edge and nose cap of hypersonic spacecrafts, reusable space vehicles andso on. In the paper, 2D carbon fiber cloth reinforced silicon carbide-tantalum carbide (2D SiC-TaC)UHTCC was fabricated by slurry-pasting and precursor infiltration pyrolysis process (PIP). Influences ofthe volume ratio (10, 20, 30, 60, 80 and 100%) of TaC powder on mechanical properties and ablativeresistance of 2D C/SiC-TaC composites were studied. The results showed that the relative density ofcomposites with 60vol% TaC powder was the highest, the flexural strength of the composites reached356MPa and the mass loss rate and recession rate were 0.0116g/s and 0.026mm/s respectively, whilethose of C/SiC composites were 0.0166g/s and 0.062mm/s respectively. Moreover, the higher TaCpowder content, the smaller the fracture toughness of the composites was. The fracture toughness of the2D C/SiC-TaC composites with 100vol% TaC powder was only 8.69 MPa-m1/2, while that of C/SiCcomposites was over 15.0 MPa-m1/2
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.368-372.1771.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanical Properties and Microstructure of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/(W, Ti)C Nanocomposite (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 368-372 (Feb. 2008), p. 717-720 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Al2O3/(W, Ti)C nanocomposite was fabricated by hot pressing technique at 1650-1700°Cunder 30MPa for 10min. The fracture toughness remarkably increased by adding nano-scale Al2O3 (11vol%) particles into Al2O3 matrix. The flexural strength, fracture toughness and Vickers hardness are 840MPa, 6.55 MPa•m1/ 2 and 20.1 GPa, respectively. The microstructure of the nanocomposite ishomogenous skeleton structure. Nano particles could refine matrix grains and lead to the crack deflectionas well as branching and bridging. The coexistence of nano-scale Al2O3, micro-scale Al2O3 and (W, Ti)Ccan reduce the sintering temperature and sintering time as well as the grain size, and improve thedensification and mechanical properties of materials
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.368-372.717.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Preparation and Properties of 2D Carbon Cloth Reinforced Ultra-High Temperature Ceramic Matrix Composites (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 368-372 (Feb. 2008), p. 1050-1052 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper the preparation of carbon fiber reinforced ultra-high temperature ceramic matrixcomposites was reported. Polymer infiltration and pyrolysis process was used to prepare 2D C/TaC-SiC,C/NbC-SiC, and C/ZrC-SiC composites. The fracture strengths of all the samples were around 300MPaand toughness around 10MPa-m1/2. Standard oxyacetylene torch tests (〉3000°C, 30s) showed that theminimum ablative rate of 2D C/SiC-ZrC was as low as 0.026 mm/s, much smaller than that of 2D C/SiCcomposites (0.088mm/s)
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.368-372.1050.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Three-dimensional skeleton and centerline generation based on an approximate minimum distance field (1998)
    Springer
    The visual computer 14 (1998), S. 303-314 
    Details
    ISSN: 1432-2315
    Keywords: Key words: 3D skeleton and centerline ; Volume visualization ; Navigation ; Distance transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003710050142
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  • 10
    Electronic Resource
    Electronic Resource
    Development of Some New Porous Metal Materials (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 534-536 (Jan. 2007), p. 949-952 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Porous metal materials have been widely used in various industrial fields in the world.This paper describes the recent research achievements of CISRI in the development of porous metalmaterials. High performance porous metal materials, such as large dimensional and structurecomplicated porous metal aeration cones and tube, sub-micron asymmetric composite porous metal,metallic membrane, metallic catalytic filter elements, lotus-type porous materials, etc, have beendeveloped
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/14/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.534-536.949.pdf
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